Combination Vehicles Practice Test

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1) To avoid steering problems because of friction between tractor and trailer, the fifth wheel should be _______ more often.

Correct! Wrong!

B. The fifth wheel should be lubricated to avoid steering problems. Greasing will also help the fifth wheel to operate smoothly. However, greasing is not the only maintenance needed for a fifth wheel, it is also important to check the fifth wheel for damage.

2) With both engine and brakes off, the loss rate should be less than ___ psi in one minute for combination vehicles.

Correct! Wrong!

C. When testing the air leakage rate for combination vehicles, the loss rate should be less than 3 psi of air in one minute.

3) When driving, the best way to notice that the trailer has started to skid is by seeing it in your mirrors. But the question is, how can you avoid skids?

Correct! Wrong!

D. A, B, and C are all correct. All of them are ways on how to avoid skidding your truck. It is important to know these techniques to prevent possible accidents.

4) When uncoupling a combination vehicle, the first thing you need to do is position the rig, now what's next?

Correct! Wrong!

B. After positioning the rig, the next thing you need to do is to ease pressure on the locking jaws. Lock the trailer brakes by turning off the trailer air supply and then back up slowly to reduce pressure on the fifth wheel locking jaws. While the tractor is pressing against the kingpin, engage the parking brakes. This holds the vehicle in place While keeping pressure off the locking jaws.

5) What is the part of the emergency air line to the trailer?

Correct! Wrong!

C. The emergency air line supplies air to the trailer air tanks and controls the emergency brakes on combination vehicles.

6) To keep dirt out of the lines, trailer _______ should be locked together or attached to "dead end" or dummy couplers when not in use.

Correct! Wrong!

C. Some vehicles have “dead end” or dummy couplers to which the hose couplers or glad hands may be attached when they are not in use. This will prevent water and dirt from getting into the coupler and the airlines.

7) There should be no visible space between the upper and lower __________ during the inspection of the combination vehicle.

Correct! Wrong!

A. When inspecting a combination vehicle, you should see no space between the upper and lower fifth wheel.

8) Peter is coupling a tractor to a semitrailer. He hooked up the emergency and air supply control lines before backing the trailer. Is that correct?

Correct! Wrong!

B. He did wrong because emergency and service air lines are the ones to be connected to do correct coupling. Air supply control does not need to hook up.

9) What will happen if you drive with the landing gear only part way up?

Please select 2 correct answers

Correct! Wrong!

Both B and C. When driving, always raise the landing gear all the way up, not only part way up. Failing to do so will cause unexpected accidents and the landing gear may catch on railroad tracks or other things.

10) What is likely to happen if the emergency line has a major leak?

Correct! Wrong!

A. If the emergency line has a major leak, it will cause the tractor protection valve to close and the trailer emergency brakes to come on. The air loss from the leak will LOWER the air tank pressure quickly.

11) A trailer hand valve should be used for parking. This statement is:

Correct! Wrong!

B. You should never use the trailer hand valve for parking because all the air might leak out causing the brakes in trailers that do not have spring brakes to unlock. The trailer hand valve should be used only to test the trailer brake.

12) While Dave is driving, he recognized that the trailer began to skid. What should he do?

Correct! Wrong!

B. Dave should stop using the brake. He should release the brakes to get the traction back. Choice (A) is incorrect since the trailer hand drive is only used to test the trailer brake. Choice (C) and (D) are incorrect too.

13) _______ are used in the service and supply air lines at the _____ of the trailers to tow other trailers.

Correct! Wrong!

C. Shut-off valves are used in the service and supply air lines at the back of trailers used to tow other trailers. These valves permit closing the air lines off when another trailer is not being towed.

14) Which of the following is not true about inspecting the coupling?

Correct! Wrong!

B. In inspecting the coupling, always check that the fifth wheel jaws have closed around the SHANK of the kingpin.

15) Wheel chocks are used for:

Correct! Wrong!

C. When parking, wheel chocks are used to hold the vehicle in place. Without it, the vehicle could roll and cause damage or injuries. Always use wheel chocks especially if the trailer has no spring brakes.

16) When uncoupling, close the air shut-off valve at the ______ of the first trailer and on the dolly.

Correct! Wrong!

A. When uncoupling, close the air shut-off valve at the rear of the first trailer and on the dolly.

17) Which image below shows the correct way of loading cargo to avoid skid and rollover.

Correct! Wrong!

B. In loading a cargo, poor weight balance can make vehicle handling unsafe. A high center of gravity causes a greater chance of rollover and you can avoid it by balancing the weight of the load well.

18) When coupling, colors are sometimes used to avoid mistakes. What is the color of the line for the emergency (supply) lines?

Correct! Wrong!

C. Red lines are for emergency (supply) lines while Blue lines are for the service line.

19) At what angle does the tow seals are pressed together in connecting the glands?

Correct! Wrong!

B. To connect the glands, the tow seals are pressed together with the couplers at a 90-degree angle.

20) Peter is a rig driver. But today, he is tasked to drive a bobtail tractor to the warehouse. His co-worker reminded him to be extra careful when bobtailing. What do you think is the reason?

Correct! Wrong!

A. Tests have shown that bobtails can be very hard to top smoothly. It takes them longer to stop than a tractor-semitrailer loaded to maximum gross weight.

21) Why you should never back up the trailer at an angle?

Correct! Wrong!

B. You should never backup the trailer at an angle when coupling a semitrailer because this may push the trailer sideways and break the landing gear. You should back the tractor up directly in front of the trailer instead.

22) Air tanks on trailers and converter dollies are filled by the emergency supply line from the tractor.

Correct! Wrong!

A. Each trailer and converter dolly have one or more air tanks. They are filled by the emergency (supply) line from the tractor.

23) When the low air pressure warning light and buzzer first come on, what should you do?

Correct! Wrong!

C. When the low air pressure warning light and buzzer first come on, bring the vehicle to a safe right away, while you still have control of the brakes. The braking power of spring brakes depends on the brakes being in adjustment. If the brakes are not adjusted properly, neither the regular brakes nor the emergency/ parking brakes will work right.

24) Which statement is not true about ABS.

Correct! Wrong!

D. Remember, if ABS malfunctions, you still have your regular brakes.

25) What is the important function of the tractor protection valve?

Correct! Wrong!

A. The tractor protection valve keeps the air in the tractor or truck if the trailer breaks away or develops a bad leak.

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